US4122495A - Method and a device for an electro-acoustic reading of an optical device image - Google Patents

Method and a device for an electro-acoustic reading of an optical device image Download PDF

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Publication number
US4122495A
US4122495A US05/791,016 US79101677A US4122495A US 4122495 A US4122495 A US 4122495A US 79101677 A US79101677 A US 79101677A US 4122495 A US4122495 A US 4122495A
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wave
image
interaction
medium
reading
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US05/791,016
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Philippe Defranould
Charles Maerfeld
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Thales SA
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Thomson CSF SA
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N3/00—Scanning details of television systems; Combination thereof with generation of supply voltages
    • H04N3/10—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical

Definitions

  • This invention relates to a method and a device for reading an optical image using acoustic waves.
  • the reading of images by means of acoustic waves is generally effected by means of non-linear interactions between two electrical fields in a semiconductor, these electrical fields being the fields associated with the deformations of a piezoelectric crystal at the surface of which elastic waves propagated.
  • the signal representing this interaction may be the electrical current which arises out of this interaction and which flows through the semiconductor.
  • the image to be read is projected onto the semiconductor where, by spatially modulating the conductivity thereof, it modulates the intensity of the signal resulting from the non-linear interaction.
  • the object of the present invention is considerably to increase this sensitivity by effecting reading in two separate steps.
  • a method for reading of an optical image by means of an electro-acoustic device said device being of a type that comprises piezoelectric medium and a semiconductive and photosensitive medium coupled with the piezoelectric medium, said image being projected onto said semiconductive medium over an interaction surface and producing a modulation of conductivity therein by photo-electric effect, at least one first electromechanical transducer generating from electrical signals elastic waves propagated at the surface of the piezoelectric medium, and means for extracting an electrical output signal, said method comprising the following steps:
  • a SECOND INTERACTION IS OBTAINED BETWEEN SAID CHARGE DISTRIBUTION AND A THIRD ELASTIC WAVE OF WHICH THE FREQUENCY CORRESPONDS TO THE SPATIAL PERIODICITY OF SAID CHARGE DISTRIBUTION, SAID SECOND INTERACTION PRODUCING A SPATIALLY UNIFORM ELECTRICAL READING SIGNAL REPRESENTING SAID CHARGE DISTRIBUTION MODULATED BY SAID IMAGE DURING THE TIME SEPARATING THE TWO PHASES, SAID READING SIGNAL CONSTITUTING SAID OUTPUT SIGNAL.
  • FIG. 1 is a diagrammatic view of one embodiment of the device according to the invention.
  • FIG. 2 is a fractional section through a variant embodiment of the device illustrated in FIG. 1;
  • FIGS. 3a, b and c are diagrams of signals suitable for use in the method according to the invention.
  • the device is formed by a piezoelectric substrate 1, for example of lithium niobate, and a semiconductive and photosensitive substrate 2 separated from one another by a thin air gap 8. These two substrates are in the form of plates elongated in a direction OZ which is the propagation direction of the elastic waves at the surface of the piezoelectric substrate 1.
  • the substrate 2 is formed by a material selected in dependence upon the field of application of the device: silicon (N or P) or gallium arsenide is used for reading visible images, whilst mercury and cadmium telluride, lead and tin telluride or even indium antimonide is used for an infrared image.
  • the elastic waves are generated by means of electromechanical transducers of the type comprising comb shapped electrodes with alternate teeth, respectively 7 and 5 at one end of the substrate 1, and 6 at its other end.
  • the image to be read is projected onto the useful surface of the semiconductor 2, i.e. onto that surface which is opposite the upper surface of the piezoelectric substrate 1 where the elastic waves are propagated. These two surfaces are called “interaction surfaces” and define a zone called the “interaction zone”.
  • the image is projected (arrow L) onto the semiconductor 2 through the substrate 1.
  • An arrangement such as this is common because the piezoelectric materials available are generally more transparent than the semiconductor materials and this is particularly the case with the materials mentioned above.
  • the image L which is one-dimensional, modulates the conductivity of the semiconductor in dependence upon its spatial light intensity distribution.
  • the device illustrated in FIG. 1 further comprises two planar electrodes 3 and 4 placed on the surfaces opposite the interaction surfaces of the substrates 1 and 2, respectively.
  • electrical signals S 1 and S 2 illustrated in FIGS. 3a and 3b are applied in a first step to the transducers 5 and 6, respectively.
  • the signal S 2 has a pulsation ⁇ and a long duration ⁇ , at least equal to twice the time taken by the elastic wave to pass through the interaction zone.
  • the pulse signal S 1 applied to the transducer 5 causes the generation of an elastic wave, also called S 1 , propagated in the direction Oz.
  • This wave has the same pulsation ⁇ as S 2 and a wave vector k equal and opposite to that of S 2 .
  • the wave S 1 interacts non-linearly with the wave S 2 during its propagation in the direction Oz and the interaction signal comprises two components:
  • the value of the amplitude Q also depends upon the duration of the signal S 1 which in turn defines the elementary analysis zone of the image.
  • a second reading step an interaction is produced between the charge distribution q(z) and an elastic pulse wave S 3 which supplies a reading signal P representing the distribution q(z) and, hence, the incident image.
  • This elastic wave S 3 is generated for example from the same side as S 1 by the transducer 7 excited by an electrical signal, also called S 3 , of which the shape may be that illustrated in FIG. 3c: a pulse of amplitude A 3 and pulsation 2 ⁇ .
  • the corresponding elastic wave of pulsation 2 ⁇ and wave number 2k interacts with the charge distribution q(z) to supply, in particular, a signal of pulsation 2 ⁇ and wave number zero, i.e. spatially uniform, which may be collected between the electrodes 3 and 4 to form the signal P.
  • the amplitude of the signal P is dependent in particular upon the product of the amplitudes A 3 and Q, i.e. it represents the sequential analysis of the charge distribution q(z) during the scanning of the interaction zone by the pulse S 3 .
  • the amplitude Q(z) of the charge distribution is modulated by photo-electric effect by the incident image because, at any point, it decreases with time, but in dependence upon the illumination received on that point. This discharge phenomenon, which is very slow in darkness, becomes increasingly more rapid when the luminous intensity increases. Accordingly, a negative reading of the image is obtained.
  • the time ⁇ t may be considered as an integration time of the image.
  • FIG. 2 is a section, in the direction of the axis Oz, through a semiconductor substrate 2 on which PN diodes are formed.
  • the semiconductor substrate 2 is, for example, silicon of N-type conductivity. Diodes may be formed by the diffusion of P + zones 21 in the substrate 2. Electrical contacts are formed by metallic deposits 23 in openings formed opposite the zones 21, in an insulating layer 22 (for example silica) covering the interaction surface of the semiconductor 2.
  • insulating layer 22 for example silica
  • diodes such as these avoid the loss of the information q(z) by lateral electrical conductivity.
  • a structure corresponding to FIG. 2 was formed with a substrate 1 of lithium niobate (section YZ) and a substrate 2 of silicon with a resistivity of the order of 10 ⁇ .cm.
  • the diodes have a diameter of 5 ⁇ m with a periodicity of 12.5 ⁇ m.
  • the air gap is approximately 0.2 ⁇ m thick.
  • the signal S 1 is a pulse of duration equal to 0.2 ⁇ s, whilst the signal S 2 is a long signal with a duration of 10 ⁇ s, their frequency being 60 mc/s.
  • the periodicity of the charge distribution is thus 30 ⁇ m.
  • the decrease in the amplitude Q during the time ⁇ t is rapid, so that these values may become lower than the noise of the structure if the value selected for ⁇ t is too great.
  • This disadvantage may be reduced by increasing the values of Q obtained during the first phase. Since these values are proportional to the product of the amplitudes of the signals S 1 and S 2 , the first step may be repeated several times for substantially improving the performances of the structure, in particular in cases where fairly low reading rates are acceptable.
  • the first step consists in causing an elastic wave, such as S 2 , generated by the transducer 6 to interact with an electromagnetic rather than elastic pulse S' 1 resulting from the application between the electrodes 3 and 4 of a pulse signal, such as S 1 .
  • the second step consists in reading the charge distribution q(z) after an integration time ⁇ t of the image, by means of an elastic pulse wave of which the pulsation corresponds to the spatial periodicity of the distribution q(z), i.e. of pulsation equal to ⁇ . This gives is collected between the electrodes 3 and 4 and which constitutes the image reading signal.
  • the invention effects the one-dimensional analysis of an image. It is obvious that, by constructing a line-by-line scanning system, the invention is applicable to the reading of an optical image in two dimensions.
  • the pulse signal S 1 may be replaced by a wave S 4 of long duration equal to at least the time taken by the elastic wave to pass through the interaction zone, this wave being linearly frequency-modulated.
  • the signal S 2 remains the same as before.
  • an elastic wave identical to S 4 is used and a reading signal is obtained between the electrodes 3 and 4 which represents the Fourier transform of the projected image.
  • Signals which correspond respectively to an encoding and to a decoding may generally be used to remplace the signals S 1 and S 3 in order to obtain different signal treatments.
  • sufficiently high values are selected for the amplitudes A 1 and A 2 of the signals S 1 and S 2 for the interaction surface to be in a saturated charge state.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Facsimile Heads (AREA)
  • Solid State Image Pick-Up Elements (AREA)
  • Transforming Light Signals Into Electric Signals (AREA)
US05/791,016 1976-04-30 1977-04-26 Method and a device for an electro-acoustic reading of an optical device image Expired - Lifetime US4122495A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR7613001A FR2350020A1 (fr) 1976-04-30 1976-04-30 Dispositif acousto-electrique de lecture d'une image optique
FR7613001 1976-04-30

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US4122495A true US4122495A (en) 1978-10-24

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US (1) US4122495A (de)
DE (1) DE2719201C3 (de)
FR (1) FR2350020A1 (de)
GB (1) GB1573956A (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4281350A (en) * 1978-09-19 1981-07-28 Thomson-Csf Acoustoelectric device for reading or processing a two-dimensional optical image
US4389590A (en) * 1981-08-26 1983-06-21 The United States Of America As Represented By The Secretary Of The Navy System for recording waveforms using spatial dispersion
US4633285A (en) * 1982-08-10 1986-12-30 University Of Illinois Acoustic charge transport device and method
US4990814A (en) * 1989-11-13 1991-02-05 United Technologies Corporation Separated substrate acoustic charge transport device
US20060033039A1 (en) * 2004-08-12 2006-02-16 Williams John R Photo-controlled luminescence sensor system
US20090018432A1 (en) * 2005-05-11 2009-01-15 Bin He Methods and apparatus for imaging with magnetic induction
US11032011B2 (en) * 2017-04-06 2021-06-08 Arizona Board Of Regents On Behalf Of The University Of Arizona Systems and methods for a quantum-analogue computer

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3826866A (en) * 1973-04-16 1974-07-30 Univ Leland Stanford Junior Method and system for acousto-electric scanning

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3826866A (en) * 1973-04-16 1974-07-30 Univ Leland Stanford Junior Method and system for acousto-electric scanning

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4281350A (en) * 1978-09-19 1981-07-28 Thomson-Csf Acoustoelectric device for reading or processing a two-dimensional optical image
US4389590A (en) * 1981-08-26 1983-06-21 The United States Of America As Represented By The Secretary Of The Navy System for recording waveforms using spatial dispersion
US4633285A (en) * 1982-08-10 1986-12-30 University Of Illinois Acoustic charge transport device and method
US4990814A (en) * 1989-11-13 1991-02-05 United Technologies Corporation Separated substrate acoustic charge transport device
US20060033039A1 (en) * 2004-08-12 2006-02-16 Williams John R Photo-controlled luminescence sensor system
US20090018432A1 (en) * 2005-05-11 2009-01-15 Bin He Methods and apparatus for imaging with magnetic induction
US9411033B2 (en) * 2005-05-11 2016-08-09 Regents Of The University Of Minnesota Methods and apparatus for imaging with magnetic induction
US11032011B2 (en) * 2017-04-06 2021-06-08 Arizona Board Of Regents On Behalf Of The University Of Arizona Systems and methods for a quantum-analogue computer

Also Published As

Publication number Publication date
GB1573956A (en) 1980-08-28
FR2350020B1 (de) 1980-05-30
DE2719201C3 (de) 1979-07-26
DE2719201A1 (de) 1977-11-10
FR2350020A1 (fr) 1977-11-25
DE2719201B2 (de) 1978-11-30

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